As generally known from the practice, in automatic transmissions with hydraulically actuated switching components, which usually have a switching piston installed in a piston space on a disc set to carry out a gearshift, the switching component is first filled with oil before the switching piston is placed on the disc set. If the switching component is disengaged, the pressurized medium is removed from the switching component and the disc set is again relaxed. The filling and installation of a switching component has a rapid filling phase in which the switching component that is almost full or running partly empty is filled with oil, there follows a filling equalizing phase during which a switching piston is placed on the disc set. At the end of the filling equalizing phase follows a pressure increasing phase which can be reproduced as pressure ramp increasing in the course of time. During this pressure increasing phase or pressure ramp the discs are adequately pressed together and can transmit or receive a torque.
It also is generally known that in a first range up to the beginning of the pressure ramp a turbine belonging to a hydraulic start component of the transmission rotates at the idling speed of an engine connected with the transmission. When the pressure ramp has been climbed, the speed of the turbine goes back to zero and a torque is passed, for example, to the wheels of a motor vehicle wherein a jerky process generally occurs which, as a rule, is felt as disturbing.
After the end of the pressure ramp, the pressure can be further raised, to increase torque transmission, by the switching components. The rise in pressure is effected according to what is needed.
On the other hand, when the switching component is opened, for example, the turbine begins to rotate until it reaches the engine idle speed. As a rule, the turbine can then take up in a manner such that this, in turn, is noticed by the driver as light jolt.
There have become known from testing that the gearshift operation can be made more comfortable by using switching times which are as brief as possible.
However, this raises questions, relative to safety, since in a change that is too quick, under certain circumstances, two switching components are simultaneously loaded with pressure and work against each other, causing a lock up of the transmission. This can bring about a situation critical to safety in addition to the operating comfort being greatly reduced.